The present invention relates to a method by which strips unwound from rolls are joined automatically. In the field of automatic power machines, for example, wrapping machines which utilize paper or heat-sealable strip material wound onto rolls, the need exists for one depleting roll to be replaced by a new roll without any break in continuity of the strip feed, as this would be unacceptable for correct operation of the wrapping machine.
Among the more pressing problems requiring solution in an automatic power machine of the type mentioned above is, therefore, the question of how an automatic splice may be made swiftly and accurately between the trailing end of a depleted roll of strip material and the leading end of a new roll of strip material. The prior art embraces numerous devices capable of effecting such an operation, though these tend invariably to be complicated, and therefore costly.
UK patent No. 1 316 062 discloses a splicing method that consists in affixing the leading end of a new strip to a first roller by means of an adhesive tab and then bringing the roller to bear tangentially against a guide roller over which the strip of the depleting roll runs during normal operation. Having thus positioned the roller, the depleting strip must be cut at a point preceding the splice in order to ensure that the remaining coils of the roll are not drawn into the machine together with the new strip. The cut must necessarily be made at a certain distance preceding the point at which the adhesive tab is brought to bear, so as to prevent the blade from entering into contact with the two rollers and with the leading end of the new strip. It is therefore typical of a roll changer device as outlined above that, on completion of the splicing operation, one is left with a double thickness of strip which appears relatively long when compared with the dimensions of the adhesive tab, and more particularly, with a substantially free length of material (restrained only at one end), namely the final waste portion of the fully depleted roll of strip, occupying an area near to where the splicing operation takes place.
This same free length of material can give rise to significant drawbacks, proving difficult to control as the strip is advanced, and, during subsequent operations by which the continuous strip is divided into single wrapping sheets, generating duplicate sheets of waste material that can impede correct operation and even cause the machine to shut off altogether.
The object of the present invention is to provide a method of splicing two strips automatically, both inexpensively and without the drawbacks mentioned above.